For a conventional driving force controller for an electric vehicle, a motor torque command value set based on a request from a driver (target driving force) is corrected to suppress a vibration (a torsional vibration) generated from a torsion of a drive system. For example, the driving force controller calculates vehicle speed as target vehicle speed, vehicle speed which is obtained when a motor torque command value is applied to an ideal vehicle model in which a drive system is assumed to be a rigid body that does not generate torsion. Then, the driving force controller obtains deviation between the target vehicle speed and actual vehicle speed, and calculates a correction value to reduce the deviation. The driving force controller thus obtains a final motor torque command value by adding the correction value to the motor torque command value.
In the conventional ideal vehicle model, disturbance torque such as: running resistance torque such as air resistance; and braking torque caused by braking, is not inputted. Thus, such disturbance torque is not reflected on the target vehicle speed outputted from the vehicle model and the correction value computed based on the target vehicle speed. As a result, although the torsional vibration can be suppressed by the correction value, there is a problem that the request from the driver and actual driving force are diverged because, at moments of running resistance generation and braking, such excessive driving force is generated as to cancel out the running resistance torque or the braking torque caused by braking.
As a method for suppressing such increase of the driving force resulting from the disturbance torque, an external input estimator has been proposed for estimating the disturbance torque, subtracting the disturbance torque from motor request torque in advance when computing the target vehicle speed, and computing the target vehicle speed with the disturbance torque taken into consideration (see Patent Literature 1).